A Michigan woman overcame almost insurmountable odds last week and gave birth to twin girls, one from each of her two wombs.
"It was just a shock," said Sarah Reinfelder, 21, mother of the twin daughters Kaylin Joy and Valerie Marie.
The chances of a successful pregnancy such as hers is about one in 5 million, according to Reinfelder's physician Dr. Connie Hedmark, an obstetrician and gynecologist at Marquette General Hospital in northern Michigan, where the twins were delivered seven weeks premature.
"We were concerned that the quality of each uterus was not good enough to carry the pregnancy," Hedmark said.
Reinfelder discovered she had two uteri, known as a Mullerian abnormality, after she miscarried her first pregnancy in March 2007, another set of twins gestating in her two wombs.
After the miscarriage and the discovery of her abnormal uterus, Reinfelder and her husband were told they were unlikely to be able to have children. But Reinfelder became pregnant again and gave birth to a son about 10 months ago.
While that pregnancy was a surprise, news that Reinfelder was pregnant with twins again was a shock. Still, the couple stayed calm about it.
"It was hard for us since we'd already miscarried," said Reinfelder, who lives in Sault Ste. Marie, Mich. "It was hard to let ourselves get excited about it."
Reinfelder's doctors took a similar approach to the natural pregnancy.
"We did not expect that it would go this far," said Dr. Breanna Pond, an obstetrician and gynecologist at Marquette General Hospital who also helped deliver Reinfelder's twins. Pond said they were prepared for a miscarriage in at least one uterus, if not both.
Womb abnormalities are not uncommon. Hedmark said that about 4 percent of all women have some sort of reproductive malformation, including having two uteri, two cervixes or a septum dividing the vaginal canal.
Womb abnormalities come in all kinds and they make it more difficult to have children for a variety of reasons.
Reproductive malformations are associated with higher incidence of infertility, miscarriage, preterm labor and breech babies, as well as other risks. For example, if one uterus goes into labor, preterm labor could be induced in the other uterus.
And a premature baby comes with its own set of risk factors, as does having a Caesarean section, which women with malformations typically opt for in lieu of a more complicated vaginal birth.
"We know there's a high rate of [problems] but it's not known why," said Dr. Richard J. Paulson, chief of reproductive endocrinology and infertility at the University of Southern California Keck School of Medicine in Los Angeles. "It's not impossible but it makes it more complex."
Experts theorize that the odd shape of the womb may be the root of potential reproductive complications.
"There is only so much tissue designated to become a uterus," Hedmark said. "When that gets shared ... they don't have normal muscle quality sometimes."
Thinner uterine walls mean the muscle may not stretch correctly or be strong enough to carry a baby. In addition, the abnormal shape could affect blood flow to the fetus.
"It's just crowded," Hedmark said. "You get a cramped situation where the baby just doesn't have much room."